Chemical risks are inevitable during the use of chemicals, because they have more or less hazards. While a strict safety management is necessitated in industrial processes, universities have many difficulties to conduct organizational management of chemical risks due to the characteristics of the research activities in university; no employment relationship with the users, i.e., students, the change of all members every a few years, and the diversity of the usage of chemicals on research topics. In this study, quantitative assessment methods are applied into the chemical risk management in universities with actual data on site. Through the interpretation of visualized chemical risks for decision making in laboratories, the role of assessment methods in risk management was discussed. Eleven solvents generally utilized in universities were taken up as the examples for risk identification. Regarding four solvents, life cycle and risk assessments were conducted for quantifying environmental impacts and workers' health risks. The quantification and visualization by such assessment methods can provide transparent indicators for chemical risk managements. The combination of existing assessment methods can facilitate the comprehensive risk analysis including laboratory-specific and generic aspects of chemical risks.
Mercury-containing wastewater from universities needs to be handled carefully in order to prevent the contamination of the surrounding environment and to reduce the high cost for its proper disposal.In this study, a practical system to reduce the volume of mercury-containing wastewater, which can be used in laboratories, was proposed and reduce the cost of waste-water treatment was achieved. Mercury ion in wastewater is vaporized by bubbling with air after the addition of a reductant. The vaporized mercury is then trapped and concentrated in a KMnO4 solution. In this study, the concentration of the KMnO4 solution, selection of the reductant, volume of the reductant solution, aeration flow rate, and bubbling time were investigated. Recovery of mercury was observed to be >90% for a 0.01-0.1% 10-mL KMnO4 solution. Thus, 0.1% KMnO4 solution was used as the mercury-collecting solution. Among the examined reductants, including NaBH4, NH2OH·HCl, and SnCl2, SnCl2 was found to be suitable for treating strong acidic wastewater. The flow rate and bubbling time were investigated for 500 mL of the sample solution. After the addition of SnC12 to the sample in a reaction vessel, almost all of the mercury in the sample solution was vaporized and trapped in the KMnO4 solution via bubbling with air at 0.4 L/min for 30 min. Based on these results, a system that reduces the volume of wastewater containing mercury was installed in a laboratory; it was confirmed that approximately 20 L of waste water can be reduced to 10 mL using this system.
Calcium hydrogen phosphate dihydrate (DCPD) reacts with fluoride ion in an aqueous solution and forms stable fluorapatite (FAp).In previous studies, we have found that the reaction of DCPD is applicable to treatment of fluoride in waste water efficiently and economically. However, release of phosphate ions from the reaction of DCPD is serious problem for the application of DCPD to waste water treatment. Previously, we developed addition of calcium carbonate was effective to decrease of phosphate ions concentration in the treated water, but the mechanism of controlling phosphate ions and suitable conditions are not cleared. In this paper, we investigated the effect of addition of calcium salts on the inhibition of the release of phosphate ions from the reaction of DCPD by analyzing the mechanism of phosphate release and the effect addition of calcium ion in reaction of the DCPD with fluoride ion. We found that increasing calcium ion concentration in the solution was effective to inhibit dissolving DCPD in initial periods, and that controlling pH value between 8 to 9 had an effect for the inhabitation of the release of phosphate ions from the reaction of DCPD. We found that addition of calcium carbonate in the reaction of DCPD was effective for both of suppling calcium ion and controlling value of pH. From the results, it was concluded that usage of DCPD under controlling pH and calcium concentration was useful for treatment of fluoride in waste water.
Participation of local residents and their cooperative relation are indispensable to environmental activities such as classification or sorting of household waste in the area or community. In order to develop such cooperation and network in a community, it is believed that "trust" shall play an important role. In this study, the actual situation and a role of the trust that supported an area network for a waste bank activity operated voluntarily by community people is studied. As a result, it is identified that the community network concerned to the waste bank activity is supported by the trust which has been brought about by existing network such as the residents' association and the women's association. In order to further expand the waste bank activities, it is thought that another action to develop new network is necessary.
The aim of this study is to investigate the monthly variation of nitrogen concentration and nitrogen mass balance in the Shira river basin, Kumamoto. The average concentration of total nitrogen was 1.11±0.34 mg L−1 (n = 205), ammonium was 0.084±0.12 mg L−1 (n = 238), nitrate nitrogen was 0.0071±0.010 mg L−1 (n = 236) and nitrite nitrogen was 0.65±0.31 mg L−1 (n = 241). The concentrations of total nitrogen and nitrate nitrogen in the river tended to be low from June to July during the rainy season. However, the amount of nitrogen increased from June and July, and then was relatively stable from August to the next May. The amount of nitrogen in the river was estimated to be about 62±32 t/month at St.8 which is located in downstream. The input of total nitrogen in the basin was estimated at about 3010 t N, and the runoff ratio to the river was about 0.66. As a result of mass balance analysis for the agricultural land in the basin, excessive nitrogen was estimated at about 66 kg N ha−1 year−1.